An article moving through the air may be subject for icing if specific weather conditions are present. Today aerodynamic surfaces of for example rotor blades of a rotorcraft, wings of an aircraft, blades of a rear-mounted “open rotor” engine (unducted fans), etc. are protected from icing by means of anti-icing and de-icing devices arranged at or beneath the aerodynamic surface. Icing is known as an undesired phenomenon, wherein a build-up of ice takes place on the aerodynamic surface. The aerodynamic surfaces could also be comprised in aero-engine air intakes, inlet channels etc.
Composite or metallic structures of the article comprising the aerodynamic surface are thus formed with aerodynamic functions and are subjected to ice build-up on their outer surfaces under specific operational conditions. The ice build-up has a strong negative effect on the aerodynamic efficiency of the affected article. For compensating the loss of aerodynamic function (e.g. sufficient lift, low drag, low efficiency etc.) due to eventual icing, the article (wing, turbine blade etc.) is often designed oversized. However, this implies a higher weight of the article itself, which of course is not desirable for aircrafts or other airborne platforms.
Anti-icing (preventing ice to form) and de-icing (melting of already formed ice) systems are therefore required in order to ensure and maintain the sufficient aerodynamic function of the affected aerodynamic surface of the article.
Currently used ice protection systems include the use of chemical liquids before aircraft take-off, pneumatic boots that brake off formed ice when inflated, heating of aerodynamic surfaces by use of engine bleed air, resistive heating of embedded electrical wires in the article and electro-mechanic devices that subject the affected structures to short duration vibration or single high energy pulses (chock waves).
The aerodynamic surface is herein defined as the outer (wet) surface of the article. The article's structure may comprise a resin matrix made of a laminate of plies, wherein each ply comprises fibres having an orientation different from—or identical to—the fibre orientation of an adjacent ply, wherein an outer ply of the laminate forms the outer surface. The article can also be defined as a component moving relatively the air, which can be a component mainly made of metal, such as a metallic structure, and covered by a composite layer.
EP 1 873 060 discloses a hybrid electrical ice protection system solving the problem of how to reduce the amount of thermal energy needed for anti-icing and de-icing the article's aerodynamic surface depending upon an event that the aircraft is in an off-nominal power condition. Thus, by means of a control unit, an anti-ice mode being selectively reduced from a fully anti-icing mode to a partly de-icing mode, in the event of off-nominal power condition. Heaters are formed as strips which can be disposed external to the outer surface.
There is thus a need to provide a de-icing/anti-icing system including an electrical heating system with improved reliability, having heaters with a high strength and low weight. There is also a need to provide a de-icing/anti-icing system that promotes for low energy consumption.
It is desirable to provide a de-icing/anti-icing system, wherein heaters of the system can be placed at positions in the article as near the aerodynamic surface as possibly and beneath it for concentrating the heat preventing ice to form thereupon or removing ice, still not affecting the aerodynamic function (smoothness) and the structure and/or strength of the article.
It is also desirable that the system has low power consumption and that it is reliable and fail-safe in service. A need for an environmental-friendly technique is also present for reducing or eliminating aircraft de-icing ground stations using sprayed-on chemical liquids.
It is also desirable to decrease an aircraft's fuel consumption, as this is environmental friendly.
It is also desirable to provide a de-icing/anti-icing system, which allows high use temperature.
It is also desirable to achieve a cost effective and flexible manufacture of the systems heaters.
There is also a need for an article comprising an aerodynamic surface, which article can be integrated in the de-icing/anti-icing system for providing an energy-saving anti-icing and de-icing functionality and which article at the same time is cost-effective to produce.
A further object is also to eliminate the eventual drawbacks of known techniques.